Emission Control MAN B&W Two-stroke Diesel Enginesflamemarine.com/files/MANBW.pdf · MAN B&W Diesel A/S, Copenhagen, Denmark ... EGR and HAM system designs and component description

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MAN B&W Diesel A/S, Copenhagen, Denmark

Contents:

Emission ControlMAN B&W Two-stroke Diesel Engines

Page

Abstract ................................................................................. 3

Emissions ............................................................................... 4

Primary Methods ................................................................... 5

Fuel valve and nozzle optimisation and timing control ................ 5

Smoke evaluation ..................................................................... 6

Particulate emissions ................................................................ 6

Hydrocarbons (and trace organics) ........................................... 7

Sulphur content in fuel and particulates in exhaust gas ............. 7

Alpha Lubricator ....................................................................... 8

CO2 emission ........................................................................... 9

Secondary Methods .............................................................. 10

Water emulsification - NOx reduction up to 20-50%................... 10

Exhaust Gas Recirculation (EGR) and Humid Air Motor (HAM) ... 12

EGR and HAM system designs and component description ...... 13

Results from engine testing with EGR system ........................... 14

Results from engine testing with HAM system .......................... 14

NOx reduction up to 98% when using SCR ............................... 14

Retrofit Installation of SCR - Case story ............................. 17

Local Marine Emission Rules ................................................ 19

Unified Technical File ............................................................. 19

Conclusions ........................................................................... 20

References ............................................................................. 21

3

Emission ControlMAN B&W Two-stroke Diesel Engines

Abstract

The worldwide focus on fuels is gener-ally increasing because of the focus onexhaust gas emissions.

During more than 10-15 years, the au-thorities have been focused on establish-ing rules for the exhaust gas emissionsfrom marine engines, and today it seemsthat IMO Annex VI will be ratified in thecourse of 2004/2005. Hence, the ma-rine industry will be under internationalregulation.

Compliance with IMO Annex VI requiresthe engines to be within the given NO

xlevel limits documented in a technicalfile following the engine in operation.

In order to give operators a unified tech-nical file to be followed by MAN B&Wlicensees, a procedure has been devel-oped by MAN B&W and accepted bythe flag states’ representatives, theClassification Societies. The unified tech-nical file is described in a separate chapter.

Until now, local rules have been introducedfor areas such as Sweden, Norway, andthe harbour of Hamburg, where for examplea harbour-fee reduction is used as anincentive for the use of low-sulphur fuel,but with limited impact on the environment,especially with regard to emissions fromships in international operation.

A general worldwide emissions limitationseems to be the only way that all coun-tries can benefit from a reduction in emis-sions. Emission limits must follow state-of-the-art technology and the ability of themarket to adapt to such limits.

It is correct that emission limits can forcethe technology to be developed, but thenthe solution chosen will not necessarilybe the optimum one. And the systemchosen on ships built wilI, on average,stay there for the ship’s lifetime, whichcan be more than 25 years.

Methods to reduce exhaust gas emissions,and techniques such as selective cata-lytic reduction and water emulsificationare already in use on MAN B&W two-stroke engines.

The authorities have so far focused onNOx and SOx, but as soon as IMO An-nex VI has been ratified, more attentionwill be given to components from theexhaust, such as HC, particulates, COand CO2.

These considerations involve not only thefuel used and the engine design, butalso operational issues and the use ofcylinder lube oil are influencing factors.

With regard to lube oil, MAN B&W hasintroduced the so-called Alpha Lubrica-tor, which enables the operator to makea considerable reduction in the cyl. lubeoil consumption and, thereby, achieve areduction in particulate emissions.

Operational-wise, MAN B&W Diesel hasproved that when installing a two-strokeengine using HFO and a reliquefactionplant on LNG/LPG carriers, CO

2 and

SOx will be reduced and, at the same

time, there will be a remarkable reduc-tion in operational costs, as the boil-offgas will be regained as gas and put backinto the tanks.

Another operational influencing factor isthe one where reduced speed of vesselsclose to shore could reduce emissionsby approx. 20% per 10% reduction ofspeed.

The latest and most far-reaching changethat has been made over the years inour engine programme is the introductionof the electronically controlled engine.

With an electronically controlled engine,the fuel injection and exhaust gas valveactivation is fully programmable, so that

the optimum reduction of exhaust emis-sion levels can be met at all engineloads.

With turbo generator and turbo-com-pound system plants, the prime moverconcept can reduce the plant’s con-sumption of fuel and, beneficially,achieve a reduction of emissions. Theconcept utilises the high-efficiency airflow from the turbochargers for a powertake-off or power take-in system.

The next generation of emission controlsystems, which is on the drawing boardand on the test facility, involves systemsintegrated into the engines, where NO

xis reduced by operating with water inthe engine intake air, also called the HAM“Humid Air Motor” principle, and theuse of EGR (exhaust gas recirculation).

These methods, so far, look very prom-ising, and a reduction of NO

x of up to

50% and a reduction of particulatesand HC seems achievable, even thoughfinal tests and production maturing stillneed to be taken care of.

The reduction of the sulphur content inHFO is so far the most efficient methodto reduce SO

x, and this reduction has

therefore been the reason for a lot ofconsiderations from the Industry. The oilcompanies may need to change theirequipment to low-sulphur fuel produc-tion, and the shipowners could faceconsiderably higher fuel costs.

The technique for removing SOx from

engine exhaust gas on ships hasproved to be very expensive and com-plicated and does not seem to be a vi-able solution with the systems beingused today.

4

Fig. 2: NOX reduction methodsFig. 1: Flow process and typical exhaust gas composition

Another consideration for ships in ser-vice is the operation on different fuelswith different sulphur levels. Ships werepreviously designed for HFO operationonly, with relatively small tanks for distil-lates. If two fuel grades are to be used,there will be a change-over situation whenoperators change from one emissionzone to another, e.g. 4.5% sulphur to1.5% sulphur, which is the limit in thelow-sulphur restricted areas.

MAN B&W Diesel participates in a projectin the European Union concerning theuse of low-sulphur fuels and the impactof doing so on the marine industry.

Exhaust gasExhaust gasExhaust gasExhaust gasExhaust gas 13.0% O2

75.8% N2

5.2% CO2

5.35% H2O

1500 vppm NOx

600 vppm SOx

60 ppm CO 180 ppm HC 120 mg/Nm3 part.

Air 8.5 kg/kWh 21% O2

79% N2

Emissions

When talking about exhaust gas emis-sions from ships, the relevant compo-nents are NO

x, SO

x, CO, CO

2, HC, and

particulates, see Fig. 1.

So far, particulates and HC, together withNO

2 and water vapour (constituting visible

smoke) are being judged by not so accu-rate opacity measurements. At thisstage, and probably for many yearsahead, NO

x and SO

x will be the only

components that will be given interna-tional measurable limits in the marinemarket. It is expected that HC and par-ticulates will follow, but it is uncertainwhen this will happen.

The industry is still considering theoptimum methods of controlling HC andparticulates, and the method of measur-ing also remains to be agreed upon. Thesituation is different for power plants, forwhich there are often limits to all pollutingcomponents of the diesel exhaust gas.

It should be noted that pollutants are usu-ally measured as concentrations,

whereas rules are formulated as absoluteemission factors (mass per unit, time orpower) arrived at by calculation, based onthe concentration measurements.

Over the years, MAN B&W has workedwith the exhaust gas emission issue in or-der to develop means to reduce the lev-els so as to comply with limitations whichcan be expected to come.

There are, in principle, two ways to lower(NOx) emissions, viz. primary and second-ary methods.

While primary methods prevent the NOx

and other pollutants from being formed,secondary methods aim at reducing orremoving the already formed pollutants.

The most relevant proven methods forNOx reduction are: fuel valve and nozzleoptimisation, timing tuning, fuel wateremulsification, Exhaust Gas Recirculation(EGR), and Selective Catalytic Reduction(SCR), see Fig. 2.

Lube 1 g/kWh 97% HC2.5% CA0.5% S

Fuel175% g/kWh 97% HC 3% S

Heat

Work

Up to 98%reductionNOx

2) Use of water emulsion

From 20�50%NOx reduction

To comply with Tier 1EPA and IMO NO code

1) Modification ofinjection equipment

receiver

3) Use of selective catalytic reduction

SCR reactor

Exhaust gas

x

5

• Well-proven traditional fuel injection pattern and technologywith increased injection rate during the injection period.

• Variable electronically controlled timing of fuel injection andexhaust valves for lower SFOC and better performanceparameters.

• Control system offers more precise timing and therebybetter engine balance and less noise with equalized thermalload in and between cylinders, minimising the risk of prema-ture need for overhaul.

• Lower rpm possible for manoeuvring.

• Better astern and crash-stop performance.

• Improved emission characteristics, i.e. lower NOx and smokevalues at any load.

• System comprising performance monitoring for longer timebetween overhauls.

Fig. 3: S70ME-C engine control system Fig. 4: Advantages of ME-engines

Primary Methods

Fuel valve and nozzle optimisa-tion and timing control

When the engines are delivered fromthe engine builder, they have, unlessotherwise specified, been prepared tomeet the IMO speed-related NOx limitcurve. This is achieved with NOx-emis-sion-optimised fuel injection valves andnozzles and, if necessary, a slight delayin fuel injection. For the fuel valves, thenumber and size of the spray holes arethe influencing factors, whereas for HCand particulate control, the influencingfactors are the valve design and, in par-ticular, the sac volume (explained later).

Compliance with the IMO rules impliesno or a slight increase in SFOC for someengines. Therefore, the fuel consumptiontolerance has been changed for IMOcompliant engines from 3 to 5%.

Technological advances developed overthe last decade have made it possibleto commercially launch what used tobe referred to as the electronic engine.

In MAN B&W Diesel’s engine portfolio,this concept is named ME/ME-C, com-prising a range of low speed engines withthe same bore, stroke and process pa-rameters as their MC/MC-C counter-parts. The “E” range comprises engineswith on-line continuous control of thetiming of the fuel injection and exhaustvalve opening and closing, by means ofelectronic control acting via a high pres-sure hydraulic oil interface. Therefore, suchengines have no conventional camshaft.The ME-C engine is shown in Fig. 3.

The operational advantages are outlinedin Fig. 4, and particularly important, with aview to emissions, is that the on-linetiming control allows better NOx controlover a wider load range, and lower partload SFOC and soot emissions.

The next step in emission control fromIMO is expected to include a 30% fur-ther reduction from present IMO AnnexVI limits. The ME/ME-C engine alreadymeets this target, which is within theelectronic control range, see Fig. 5.

This also means more stable running,particularly at low load.

The benefits are obtained mostly in thecontrol of the fuel injection, wherethe system, with individually controlledfuel pumps with hydraulic oil activation,allows optimum fuel injection (“free”)rate shaping at any load. Hence thefuel injection pressure and, thus, injec-tion intensity is a controllable parameter,contrary to the situation on mechanicallycontrolled engines.

The independently controlled exhaustvalve timing adds to the benefit by en-suring a more optimum air supply tothe cylinders at any load condition.

The ME/ME-C engines are now gainingmonumentum in the market, and prac-tically all types are represented on thereference list, and the first seagoing en-gine featuring this principle has, with im-peccable results, logged more than 8,000hrs. on board the Norwegian chemicalcarrier M/V Bow Cecil owned by Odfjell.

6

Smoke evaluation

A traditional measure of the combustionquality, and a traditional way of qualifyingthe ‘emission’, is to look at, or to measure,the smoke intensity. The exhaust gasplume, when it leaves the top of thestack, may be visible for various reasons,e.g. due to its content of particulatematter and nitrogen dioxide, NO2 (a yel-low/brown gas), or of condensing watervapour. Although it may be argued thatthese components are either subject toseparate legislation (NOx, particulate mat-ter) or not harmful (water), it is a fact thatsmoke and/or opacity limits are tradi-tionally applied in certain countries, e.g.in the USA.

Unfortunately, methods of measuringsmoke and opacity vary, and the figuresresulting from the different methods arenot really comparable.

When considering visible emissions, weshould bear in mind that the larger theengine, the more likely it is that theexhaust gas plume will be visible. This isbecause, for a given Bosch Smoke

Fig. 6: Fuel valves for K98MC

At transient load and at low load, smokeis often visible, but typical smoke valuesfor the most recent generation of MANB&W engines are so low that the exhaustplume will be invisible, unless water vapourcondenses in the plume, producing a greyor white colour. However, the NO

2 may

give the plume a yellowish appearance.As mentioned, low and transient loadsmoke will practically disappear onelectronically controlled engines.

Particulate emissions

Particulate emissions in the exhaust gasmay originate from a number of sources:

• agglomeration of very small particles of partly burned fuel,

• partly burned lube oil,

• ash content of fuel oil and cylinder lube oil,

• sulphates and water.

The contribution from the lube oil consistsmainly of calcium compounds, viz. sul-phates and carbonates, as calcium is themain carrier of alkalinity in lube oil toneutralise sulphuric acid. Once fuel isatomised in the combustion chamber,the combustion process in a diesel en-gine involves small droplets of fuel whichevaporate, ignite, and are subsequentlyburned. During this process, a minute partof the oil will be left as a “nucleus” com-prising mainly carbon. Consequently, particu-late emission will vary substantially withfuel oil composition and with lube oil typeand dosage. It is therefore difficult to stategeneral emission rates for particulates.

In general, the particles are small, andit can be expected that over 90% willbe less than 1 µm when heavy fuel oil isused, excluding flakes of deposits, peeling-off from the combustion chamber or ex-haust system walls, which in general aremuch larger.

Number (BSN value), the greater thediameter of the plume, the greater theamount of light it will absorb. For in-stance, a BSN of 1 will mean almostinvisible exhaust gas from a truck en-gine, but visible exhaust gas from alarge, low-speed engine.

Fig. 5: Mode-change demonstration on a 7S50ME-C engine at 75% load

16:37 16:38 16:39 16:40 16:41 16:42 16:43 16:44 16:45 16:46

NOx [ppm]

2003 �02�17

1401501601701801902002102202300 020 10040 20060 30080 400100 500120 600140 700160 800

CylinderPump

2003 �02 �17

1401501601701801902002102202300 020 10040 20060 30080 400100 500120 600

700160 800

CylinderPump

Economy mode Low NO X mode

Time

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300NOx [ pm]

1401501601701801902002102202300 0

20 10040 20060 30080 400

100 500120 600140 700160 800

CylinderPump

2003�02�17

1401501601701801902002102202300 0

20 10040 20060 30080 400

100 500120 600140 700160 800

CylinderPump

Economy mode Low NOX mode

2003�02�02�17

Now usedas standard

Solid

Conventional fuel valveSac volume 1690 mm3

Slid type fuel valveSac volume 0 mm3

As at 1999.01.26

7

Fig. 7: Hydrocarbon emission, fuel valve comparison – 7S50MC-C Fig. 8: Emission of particulates as a function of fuel sulphur content

As can be seen from the measurements,the slide-type fuel valve design has quitean impact on HC and particulates.

For compliance with the IMO rules, low-NOx nozzles are used. For HC andparticulate control in general, slide-typefuel valves are used. The latest valvesfeature both the zero-sac volume andthe low-NOx spray pattern, see Fig. 6.

It should be mentioned that the IMONOx-regulation, when ratified, does notapply for ships where the keel was laidbefore January 2000.

Sulphur content in fuel andparticulates in exhaust gas

The sulphur content in fuel oil has alarge impact on the particle level in theexhaust gas. IMO has proposed re-strictions of sulphur to 1.5% in specialareas like the North Sea and the BalticSea in northern Europe, and local ma-rine emission rules, e.g. in Sweden andNorway, are aimed at reducing the par-ticulate emission substantially (see alsothe chapter regarding local marinerules). Tests and analysis of exhaustgas have shown that a high-sulphur

0

200

400

600

800

1000

604020

Conventional Slide valve

HC – ppm C1 (dry 15% O2)

Engine power � %80 100

Apart from the fact that a smoking en-gine is not a very pleasant sight, the sootfrom an engine can cause difficulties,especially if it is “wet” with oil. In suchcases, it may deposit in the exhaust gasboiler, especially on cold surfaces, thusincreasing the back pressure and repre-senting a boiler fire hazard. Combustionprocess control, together with appropriatetemperature control in the boiler, andfrequent cleaning, are the ways to avoidthis problem [4].

Hydrocarbons (and traceorganics)

During the combustion process, a verysmall part of the hydrocarbons will leavethe process unburned, and others willbe formed. These are referred to as un-burned hydrocarbons, and they are nor-mally stated in terms of equivalent CH

4content.

The content of hydrocarbons in the exhaustgas from large diesel engines depends onthe type of fuel, and the engine adjustmentand design. Reduced sac volume in the fuelvalves has greatly reduced HC emis-sions. The sac volume is the void space inthe fuel valve downstream of the closingface, as seen in Fig. 6.

HFO can give several times higher par-ticle levels than if the engine is operatedon gas oil. A large part of the differencebetween HFO and DO is related to thesulphur, which together with water formsparticulates. This is seen in Fig. 8.

Correspondingly, long time use of lower-than-average sulphur fuels will, contraryto normal marine applications, call forthe use of lower BN lube oils in ordernot to overdose the combustion cham-ber with deposit-generating additivatedoils. This will be particularly relevant forengines operated continuously at highload having less need for SOx neutra-lising on the liner surface due to hightemperature.

It has been established that a certainlevel of controlled corrosion enhanceslubrication, in that the corrosion gener-ates small “pockets” in the cylinder linerrunning face from which hydrodynamiclubrication from the oil in the pocket iscreated. The alternative, no corrosion,could lead to bore-polish and, subse-quently, hamper the creation of thenecessary oil film on the liner surface,eventually resulting in accelerated wear.

PM – emission %

100

90

80

70

60

50

40

30

20

10

0

0.2 0.8 1.4 2.0

Fuel-S %

8

Alpha Lubricator

In consequence of the above, the cylin-der oil feed rate has an impact on theparticulate emission. Tests show thatwhen reducing the cylinder oil feedrate, the particulate emission is also re-duced, see Fig. 10.

Cylinder lube oil consumption representsa large expenditure for engine operation,and the reduction of cylinder lubricationis an important development theme.The aim is to reduce the cylinder lubeoil dosage, while at the same time main-taining a satisfactory piston ring/liner wearrate and maintaining, or improving, thetime between overhauls.

MAN B&W Diesel has achieved this bydeveloping the Alpha Lubricator system,Fig. 9, which is a high-pressure elec-

Fig. 10: Particulate emission as a functionof cyl. lube oil consumption

Fig. 9: 12K98MC-C with Alpha Lubricator System

This phenomenon also occurs on trunkpiston engines where a bore-polishedcylinder liner surface hampers the func-tioning of oil scraper rings and leads toaccelerated lube oil consumption due tothe open access to the crankcase oil.Corrosion control – not avoiding corro-sion – is therefore crucial, and adjustingthe BN to the fuel oil sulphur content isessential particularly on high-loadstationary engines.

It should be considered that, irrespectiveof the sulphur content being high or low,the fuels used in low speed engines areusually low quality heavy fuels. Therefore,the cylinder oils must have full capacityin respect of detergency and dispersancy,irrespective of the BN specified. This isa newly developed technology nowmastered by the well-reputed lube oilsuppliers, who can individually tailor acylinder lube oil to the relevant fuel.

tronically controlled lubricator that injectsthe cylinder lube oil into the cylinder atthe exact position and time where the ef-fect is optimal, which is not always pos-sible with the conventional lubricators oftoday. Both for marine engines and en-gines for power generation purposes,very low feed rates have been demon-strated, with oil consumption down to0.5 g/bhph.

By applying low oil dosage as for the above,emission is lowered, and also less cylinderoil is wasted in the engine, where it couldend up in the system oil, resulting in in-creased TBN and viscosity.

0

0.1

0.2

0.3

0.4

0.5

0.6

0 0.5 1 1.5 2 2.5Cylinder lube oil consumption (g/kWh)

at 100 % MCR conditions

Particulates (EPA17)g/kWH

9

CO2 emission

Emission control has turned into the mostimportant driving force for development.

Hence, this is an area to which extensivedevelopment effort is allocated. Thisemphasises both on NO

x control, SO

xlimitation, particulate control and, to anincreasing extent, on CO

2 emission, the

latter reflecting thermal efficiency.

The so-called greenhouse effect is widelydiscussed, and the CO

2 concentration

in the atmosphere is looked at withsome anxiety. In any case, the lowspeed diesel is the heat engine availablefor ship propulsion with the lowest CO

2emission. This is possible simply by virtueof its high thermal efficiency.

One (only) field of application where theindustry has not yet taken advantage ofthe heat-efficient low speed diesel is forthe propulsion of LNG carriers. The boil-off rate of modern LNG containment sys-tems is so low that this gas, when burnedin the boiler only constitutes about 30-50% of the energy consumed to pro-duce the steam for the turbines. Therest is supplied as heavy fuel.

Fig. 12: Round trip emissions, 135,000 m3 LNG carrirer

Fig. 11: Operating costs for LNG carriers

By reliquefying the boil-off gas and return-ing it to the tanks, and by using regularheavy fuel burning low speed diesels forLNG carrier propulsion, the CO

2 emission

could be reduced by up to 30%, and thereturned gas could be sold for up to USD3.5 million per vessel per year, as seen inFig. 11.

To avoid immobilisation for overhaul of thediesel, a twin engine fully redundantpropulsion system as shown in Fig. 13is proposed. Environmental impact andeconomic savings are driving this industrytowards it.

The turbo-compound system of the twoproposed engine alternatives improvesthe plant efficiency by utilising excess airfrom the turbocharger to generate elec-tricity to the ship grid, or returning it to theengine shaft as mechanical energy.

For LNG carriers, an alternative to HFOburning engines is dual fuel ME-GI en-gines, where GI stands for ’gas injection’.If the gas price is considered to be lessvaluable than the HFO/DO used on theHFO burning engine, a ME-GI can beinstalled instead to burn the boil-off gas(BOG).

The ratio between HFO and BOG used isvariable over 30% load, and can, as such,be adjusted to the actual BOG amountavailable. This is described much more indetail in a MAN B&W Diesel paper, ref. [5].

0

2

4

6

8

10

12

14

Mill. US$/yr.

Steam

Diesel

Steam

Diesel

Steam

Diesel

Steam

Diesel

125K 150K 175K 200K

Production of electricity

Lube Oil + MaintenanceLNG consumption

HFO consumption

CO (100 ton)

SO (ton)

NO (ton)

Particles (ton)

2

x

x

0

20

40

60

80

100

120

140

160

180

Steam plant Diesel MC�GI MC�GI + SCR

Tons (100 tons for CO )2per round trip

10

Fig. 13: LNG carrier propulsion systems

Secondary Methods

Water emulsification –NOx reduction 20-50%

The NOx reducing mechanism resulting

from the introduction of water into thecombustion space is a combination ofthe water reducing the maximum peaktemperatures in the combustion processbecause of its evaporation, and the re-sulting improved atomisation of the fuel,thereby reducing the NO

x emission.

At the beginning of the 1980s, MAN B&WDiesel made tests on NO

x reduction us-

ing water-in-fuel emulsions. Before thattime the emulsifier was mostly consideredfor homogenising of fuel oil to dispersesludge and water remaining in the fuelafter centrifuging.

AlterAlterAlterAlterAlternative 1: native 1: native 1: native 1: native 1: Twin-engine solution

Main engine6S70ME�GI

Main engine6S70ME�GI

Reliquefaction plant

Boil�off gasReturn to tanksGenSet

GenSet

GenSet

With regard to NOx emissions, water emul-

sions showed a significant reduction inNO

x emission with a relatively limited

penalty in terms of fuel oil consumption.

Since 1984, long-term service experiencehas been available from a 7L90GSCApower plant engine, operating on 30%water addition, complying with local rules.

Tests have also been carried out on ourresearch engine in Copenhagen (1L42MC)and on the Spanish island of Menorca(10L67GBE-S) with ultrasonic typehomogenisers. Furthermore, tests havebeen made on a 5S60MC engine withnearly 50% water added. These testsand the service results are all satisfactory,both with regard to NO

x reduction and

engine performance.

In addition, ultrasonic homogenisingsystems for stationary plants are usedon the island of Guam. The NO

x reduc-

tion is approx. 50% with a 50% wateramount added, i.e. water constitutes33.3% of the total volume of fluid injec-ted into the engine.

The experience from the test and lateroperation fully covers the expectationswith regard to NO

x reduction and op-

eration of the units. For the two-strokeengine, we have experienced 10% NO

xreduction for each 10% water added.The water amounts refer to the injectedamount of fuel oil, see Fig. 14.

In order to have the optimal spray in thecombustion chamber, it is recommendedthat the water droplets in the fuel oil af-ter emulsification are max. 5 µm. The testresults show that this is easily obtained byusing the ultrasonic type, whereas for theearly mechanical type the size measuredwas above our recommended limit.

If the engine is to be operated on dieseloil, it may be necessary to add additivesto stabilise the media. We have tested this,and also in this case the performance wasgood. The location of the homogeniser inthe fuel oil system is shown in Fig. 15.

The addition of water to the HFO byhomogenisation increases the viscosity,as shown in Fig. 15. To keep the viscosityat the engine inlet at 10-15 cSt, max. 20cSt, it may become necessary to raisethe temperature to more than the 150oCwhich is standard today (max. 170oC at50% water) and to raise the fuel oil looppressure.

The external fuel oil pipe system followsthe Germanischer Lloyd class 1 pressure.The supply pump pressure can bechanged to ∆p = 9 bar instead of thecurrent ∆p = 4 bar.

Internally on the engine a stronger actua-tor may be needed for the governor, be-cause of the higher fuel oil supply pressure.

11

Fig. 14: Typical measured NOX reductions when using emulsified fuels

Fig. 15: Pressurised fuel oil system with homogeniser

The water used for the emulsificationhas to be distilled. It must comply withthe max. limit for fuel for salt (NaCl), asthe sodium can react with vanadium inthe fuel oil so that particles/deposits ofvanadium accumulate on the valvespindles and valve seats, thus resultingin leakages.

The water should be without other saltsas well, and be clean so that operationwill not result in fouling of injectors andexhaust gas components and boilers.

Therefore, for production of water for thewater emulsion, the most obvious sourceon board ship is the water from the fresh-water generator.

As an example, it can be mentioned thatthe theoretical amount of water which

From centrifuge

Aut. de�aerating valve

Venting box

Fresh water supply

Supplypumps

Circulatingpumps

Fullflowfilter

Fuel oildrain tank

Heavyfueloil

servicetank

Dieseloil

servicetank

Homo�genizer

Preheater

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80Water content � % mass

NO � % rel. to zero H Ox 2

12

A safety system to ensure that a changein operation does not influence the stabilityof the emulsion, and thus the reliabilityin operation, has been designed andtested by MAN B&W Diesel.

Water emulsification in connection withan electronically controlled engine (ME/ME-C) offers the additional flexibility ad-vantages:

• Optimal injection rate shaping with any water content.

• “Free rate shaping” allows the use of large water amounts even at low engine load as pre-injection can be used to compensate for a larger ignition delay.

Exhaust Gas Recirculation (EGR)and Humid Air Motor (HAM)

Modification of combustion air properties.For both the Exhaust Gas Recirculation(EGR) and the so called Humid Air Mo-tor (HAM) systems, the NO

x reduction

effect is achieved by reducing the localmaximum combustion temperatures inthe combustion chamber, and reducingthe concentration of oxygen by the ad-dition of inert media with high specificheat: exhaust gas or water vapour. TheNO

x production only takes place at very

high temperatures (2,200°K and above),and it increases exponentially with thetemperature. The EGR method is basedon a reduction of the oxygen contentin the cylinder charge, and the HAMmethod is partly based on reducing theoxygen content of the cylinder chargeand partly on increasing the heat capac-ity of the cylinder charge by the additionof water vapour.

As mentioned above, these methods(EGR and HAM) have, by calculationsand tests, proved their capability for NO

xreduction, but they have never beforebeen developed to a commercial appli-cation level for large two-stroke engines,and they have not been fully optimisedwith regard to cross-over effects on fueloil consumption, heat load conditionsand other emission parameters.

After careful evaluation of the EGR andHAM methods, we concluded that re-circulation on the high-pressure sidefrom the exhaust receiver to some-where in the scavenge air system afterthe turbocharger compressor, with assis-tance from an EGR blower, would be themost suitable EGR solution. Further-more, high-pressure side water sprayhumidification would be the most suitableHAM solution for our two-stroke engines.

can be produced by the freshwater gen-erator for an 11K90MC operating at 90%MCR load is about five times more thannecessary for 15% water emulsion, andabout 2-3 times more than necessary for33% water emulsion.

Alternatively, the water drained off fromthe water mist catchers can be used.However, the available amount dependson the humidity in the air.

The homogeniser control system mustensure that the necessary amount of wateris added to suit the amount of fuel oilactually supplied.

A micro-processor controls the additionof water so that the fuel/water emulsionalways consists of the correct amountof injected water.

A flow meter continuously controls theflow of HFO and water through thehomogeniser.

Fig. 16: Viscosity versus water percentage

1

10

1520

100

75 100 125 150 175

Temperature Co

5% water10% water18% water25% water36% water40% water

Viscosity cSt

* % water of the total injected emulsion Fuel: 380 cSt at 50 Co

13

EGR and HAM system designsand component description

Figure 17 gives a schematic overview ofthe system.

A number of EGR/HAM system con-figurations, as illustrated in Fig. 17, willbe outlined in the following.

Simple Exhaust Gas Recirculation (EGR)(green line, Fig. 17). The purpose of thisbasic high-pressure EGR system is totest the performance of the simplestpossible set-up. This EGR system con-sists of a gas line from the exhaust gasreceiver to a position just after the lastcharge air cooler, but before the last watermist catcher, so that the risk of foulingof sensitive parts is completely avoided.

In the EGR line, the simple EGR systemhas two water injection stages, with a

simple water separator unit after both,see Fig. 18. The first water injectionstage involves humidification with saltwater in order to ensure that there isno freshwater consumption in the sec-ond freshwater injection stage. The out-let temperature of the first stage is ap-proximately 100oC. This stage has asingle multi-nozzle injector.

EGR with scrubber and water treatmentWhen/if there is a demand for clean EGRgas and/or water outlet from the EGRloop, a more advanced system is required.

This system is connected to the exhaustsystem in the same way as the simple EGRsystem, but the EGR line is routed to a“bubble-bath” scrubber from the Canadiancompany DME (EcoSilencer, ref. Fig. 19),which cleans and cools the exhaust gas.

Fig. 18: Design principle of the simple EGR unitFig. 17: Schematic design of EGR and HAM systems application on the 4T50ME-X engine

Diesel engine

Line for simple EGR

Line for simple EGR

Exhaustgasscrubber

Non return valve

WMC

WMC

Spray

Spray SW

FWWMC

WMC

SW

FWWMC

Spray

Spray

EGRblower

Auxiliaryblower

CoolerNo. 1 +No. 2

SW

The water loop in the scrubber system iscooled and monitored in a Water Treat-ment Skid from DME (ref. Fig. 19) with afilter and settling system, cleaning theused sea water.

Combustion air humidification (HumidAir Motor – HAM) (red line Fig. 17). Withthis system, the engine runs with saturatedscavenge air at higher temperatures thana standard engine, because the con-ventional inter-cooling is replaced by waterspray evaporation/cooling, just after theTC compressor, until the wet-bulb or lowertemperature for the hot compressor out-let air is reached.

If/when a scavenge air temperature ofapprox. 70 °C is acceptable, no conven-tional scavenge air cooler is necessary,and only a relatively simple spray humi-difier system is required.

Coldexhaustgas outlet

1st stageFlow change cyclonewaterseparator

2nd StageFlow change cyclonewaterseparator

Hot exhaustgas inlet

Freshwaterinjectors

Freshwaterdrain

Seawaterinjectors

Freshwater drain

14

Results from engine testingwith EGR systems

Very promising operating conditions havebeen obtained during the tests, as outlinedin the below summary of the main results.

Emission results. The relative changesin measured emission parameters as afunction of the recirculation amount at75% engine load are illustrated in Fig. 20.As can be seen, at increased recircula-tion amounts, the HC and PM emissionsare reduced corresponding to the reduc-tion of the exhaust gas flow from theengine.

This indicates that each engine cyclehas the same production of HC and PMindependent of the recirculation amount,and that the HC and PM in the recircu-lation gas is eliminated during the normalcombustion process.

The increase in CO emissions with in-creased recirculation amount indicates,as expected, that the lower cylinder ex-cess air ratios at increased recirculationamount result in larger local regions in

Results from engine testingwith HAM systems

As for the EGR system also for theHAM system very promising operatingconditions have been obtained, as out-lined in the following.

Emission results. The measured emissionparameters, as a function of the HAMlevel at 100% engine load, are illustratedin Fig. 22. As can be noted, the HC andPM emissions are nearly unaffected bythe HAM level. The CO emissions increasesignificantly with increased HAM level,most likely due to the lower cylinder ex-cess air ratios at increased HAM levels,which result in larger local regions in thecombustion chamber with lack of oxy-gen. Furthermore, the expected signifi-cant reduction of the NO

x level has

been confirmed.

the combustion chamber with lack ofoxygen. Furthermore, the expected sig-nificant reduction of the NOx level hasbeen confirmed.

Cleaning the exhaust gas with scrubber.As mentioned in the description of theEGR system, the EcoSilencer has beenintroduced in the EGR system to cleanthe exhaust gas and, if possible, also toreduce some of the emission compo-nents. MAN B&W Diesel has accord-ingly measured the emission compo-nents at inlet and outlet of the scrubberat different engine loads.

The results from these measurementsindicate that scrubbing reduces PMemission to 20-25% (highest at lowloads and lowest at high loads) and thatHC and CO pass the scrubber nearly un-affected. The NO2 fraction of the NOx is,as expected, dissolved in the water,and the NO fraction of the NOx passesthe scrubber nearly unaffected. Fig. 21shows a picture of the filters used fordilution tunnel PM measurements takenbefore and after the scrubber at 75%load and 15% recirculation.

Fig. 19: “Bubble-bath” scrubber (EcoSilencer) and Water Treatment Skid from DME

NOx reduction up to 98%when using SCR

To reduce the NOx level by up to 98%, it

is necessary to make use of the SCR(Selective Catalytic Reduction) technique.

With this method, the exhaust gas ismixed with ammonia NH

3 or urea (as

NH3 carrier) before passing through a

layer of a special catalyst at a tempera-ture between 300 and 400°C, wherebyNO

x is reduced to N

2 and H

2O.

The reactions are, in principle, the fol-lowing:

4NO + 4NH3 + O

2 → 4N

2 + 6H

2O

6NO2 + 8NH

3 → 7N

2 + 12H

2O

NOx reduction by means of SCR can only

take place in the mentioned temperaturewindow, because if the temperature istoo high, NH

3 will burn rather than react

with the NO/NO2. At too low a tempera-

ture, the reaction rate would be too low,and condensation of ammonium sulphateswould destroy the catalyst.

Freshwater

Seawater

Cooling water

Clean brine

Sludge out

Wastepump

Sludgetank

Recirculatingpump

Supply pump

Water supply / Cooling water / Water brineCirculating waterSludge

ScrubberEcoSilencer

Hot exhaustgas in

Exhaustgas out

15

Fig. 20: Emission parameters at 75% load at various EGR ratios Fig. 22: Emission parameters at 100% load as a function of scavengeair humidity

Fig. 21: PM on filters before and after scrubber

Before scrubber After scubber

The amount of NH3 injected into theexhaust gas is controlled by a processcomputer dosing the NH3 in proportionto the NOx produced by the engine asa function of the engine load. The relation-ship between the NOx produced and theengine load is measured during test runson the engine testbed. The relationshipobtained is programmed into the processcomputer and used for the feed-forwardcontrol of the NH3 dosage. The ammoniadosage is subsequently adjusted for biasby a feed-back system on the basis ofthe measured NOx outlet signal.

The catalyst has a monolithic structure,which means that it consists of blocksof catalyst with a large number of paral-lel channels, the walls of which are cataly-tically active. The channel diameter hasan influence on the pressure drop across

the catalyst as well as on the risk ofdeposits on the catalyst. The channeldiameter is optimised according to thedust content, the composition of theexhaust gas, and the permissible pressuredrop across the SCR reactor.

Absolute humidity (vol./vol.) of scavenge air in %

110

95

100

90

300

200

100

100

80

60

Change in %

PM

HC

CO

NOx

0 3 6 9

120

zero half full

100

100

90

80

100

90

200

100

80

60

150

EGR ratio in %

Relative change in %

0 105 15 20

NOx

CO

HC

PM

40

Fig. 23: SCR flow chart

By�pass valve V1

Turbocharger

SCRReactor

Engineproper

Exhaustgas

AirAuxiliaryblower

16

used when the vessels in regular tradeare in the San Francisco Bay area. Thesystems have performed to specifica-tion ever since installed. No reduction inefficiency due to use or ageing is re-ported. Fig. 23 shows the SCR flowchart, and Fig. 24 the actual systemlayout on the 6S50MC. Fig. 25 is thecurrent reference list.

High-efficiency turbochargers have to beused. The exhaust gas temperature mea-sured is slightly higher than for engineswithout SCR because of the ammonia/urea heat release in the SCR process.

The SCR reactor is designed as a semi-rectangular pressure vessel for horizon-tal or vertical installation and flow. As anexample, the following main dimensions(excl. support structure and insulation)are for an 11K90MC engine:

Diameter, m : 2.4Height, m : 4.5Length, m : 15Weight, incl. catalyst, tons : 42

The design and dimensions of an SCRreactor are influenced by the exhaustgas flow, the exhaust gas temperaturewindow, and the NOx reduction rate.

The optimum, and most common solution,therefore, is that the SCR reactor is tai-lor-made for a specific installation and itis, of course, more convenient to build-inthe SCR during the construction of theship. Retrofit is also possible, though.

The space requirement for an SCR unitin the engine room is considerable, ontop of which the piping and the mixerbetween the engine and the SCR cata-lyst also require a lot of space, so thedesigner’s task is to make the SCRsystem as compact as possible while,at the same time, ensuring easy accessfor maintenance and operation.

As can be seen in Fig. 26, we have ex-amined a number of alternative designsof SCR reactors.

Fig. 25: SCR reference list for MC engines

1 6S50MC ship NOX reduction 93-95%

2 6S50MC ship NOX reduction 93-95%

3 6S50MC ship NOX reduction 93-95%

4 6S50MC ship NOX reduction 93-95%

5 9K80MC-GI-S power plant NOX reduction up to 98%

6 4L35MC-S power plant NOX reduction > 93%

7 2x7K60MC-S power plant NOX reduction > 93%

8 6S35MC ship NOX reduction > 93%

Fig. 24: SCR system layout

In collaboration with the Danish chemicalengineering company of Haldor TopsøeA/S, MAN B&W Diesel has developedthis method – well known from industrialapplications – for use on diesel engines.

Four vessels with 6S50MC engineswere equipped with SCR catalysts forNO

x reduction of 93-95%. The first ship

was commissioned in 1989 and the lastship in 1994. The systems installed are

Engine

Preheating and sealing air

High�efficiency turbocharger

1

3

NO and O analysersx 2

2

Orifice

Air

Staticmixer

Air outlet Air intakeSCR reactor

Exhaust gas outletDeck

EvaporatorAmmonia

tank

Processcomputer

Air

Support

17

If ammonia is used as the medium fordeNOx, the tank should be located ondeck. In the case of urea, we recom-mend that a tank within the hull struc-ture be used, to lower the cost. Havingsuch a tank in the hull will also minimisethe space requirements, comparedwith the installation of a tank on deck.

If it is not possible to find an appropriatetank on board, the tank could be builtinto containers.

We have been discussing the issue withLloyd’s and ABS, and it is fully acceptableto use and build-in the tank for urea asoutlined.

On the vessel shown in Fig. 27, the DeltaPride, the medium is ammonia NH3, andthe supply system and tank are locatedon deck in a confined space which is opento the atmosphere.

Retrofit Installation ofSCR – case story

In December 2000, an order was receivedfor the installation of an SCR unit on theNorwegian owned LPG-carrier NavionDania, equipped with a 6S35MC mainengine.

The question of installing an SCR unit onthis ship had already been raised in 1999when the ship was being built and, in orderto facilitate the possible later installation,the ship and engine were prepared byHyundai for this option, i.e. space wasmade available for the installation of anSCR reactor of the proper dimensions.

The urea storage tank was preparedand, on the engine side, the sizes ofturbochargers and auxiliary blowers werelaidout for the installation of an SCR unit.For contractual reasons, the ship had tocontinue its operations, so the majorpart of the installation work was carriedout while the ship was in operation.

Fig. 27: M/V Delta Pride, 6S50MC, with selective catalytic reduction

Fig. 26: Alternative SCR configurations

Traditional vertical SCR

Engine integrated SCR

Horizontal SCR

Partial SCR

MAN B&W Diesel patent MAN B&W Diesel patent

Korea Line Corporation

18

32

1

5

6

78

4

Deck

Prior to installation DeNOx mode with of SCR injection of urea

Engine load 75.8% 77%

Turbocharger rpm 15,600 15,700

T/C inlet temperature 440 °C 440 °C

Scavenge air pressure 2.02 barg 2.10 barg

NOx emission 1100 ppm* 132 ppm* (<2 g/kWh)

Urea consumption - 62 l/h

Fig. 28: Engine performance data

Fig. 29: M/V Navion Dania with SCR catalytic reactor installed

6S35MC, deNOx

The SCR installation work that, normally,would require off-hire was performed dur-ing the scheduled guarantee inspectionsof the vessel.

The SCR test trial was completed inJuly 2001, and the vessel has sincethen been operating with reduced NO

xemission from the main engine.

The reduction of NOx emission for the

6S35MC can be obtained between40-100% engine load, when running onHFO with a sulphur content of up to2.4%. Below 40% engine load, the in-jection of urea is stopped due to low ex-haust gas temperatures. The risk ofcreation of ammonia-sulphate is therebyavoided. Performance data are shownin Fig. 28, and the actual system layoutis shown in Fig. 29.

SCR installation on an electronicallycontrolled engine. As for NO

X reduction

by means of water emulsion, the flexibil-ity of the electronically controlled enginewill improve the emission control andoperation.

When operating with an SCR catalyst, itis difficult to maintain the engine dy-namics and the turbocharger stability attransient engine loads. However, withthe electronically controlled engine, afaster load-up by early exhaust valve

opening and late injection timing is pos-sible and, furthermore, modulated ex-haust valve timing stabilises the turbo-charger.

Hence, ME/ME-C engines and SCRsystems are very compatible.

On the M/V Navion Dania, urea is usedfor NOx reduction. The urea is stored inhull tanks.

1. SCR reactor

2. Turbocharger bypass

3. Temperature sensor after SCR

4. Large motors for auxiliary blowers

5. Urea injector

6. SCR bypass

7. Temperature sensor before SCR

8. Additional flange in exhaust gas receiver

* Measured during SCR test trial

19

Local MarineEmission Rules

On 19 May 2004, 15 countries represen-ting more than 50% of tonnage in IMOhad ratified IMO Annex VI, which willcome into force on 19 May 2005.

Countries like Sweden and Norway haveintroduced reductions in harbour feesfor ships operating on low sulphur fueland with a low NOx level, in order toencourage low pollution applications. Asimilar scheme has been introduced inHamburg.

We foresee more local rules like thesecoming up, especially if IMO furtherprolong the ratification period and enfor-cement date for new IMO regulations.

European UnionThe EU is in the process of deciding onwhich restriction limits to follow. Accord-ing to the Danish Ministry of the Environ-ment and Energy, the EU is in favour ofadopting the IMO Marpol convention,and thus expand the low-sulphur restric-ted area to include also the French coastin the English Channel, and the North Sea.

Status: Awaiting ratification of the IMOAnnex VI.

SwedenThe Swedish authorities decided to aimat a 75% emission reduction by the be-ginning of 2000. In order to reach thisgoal, the authorities apply financial in-centives in the form of environmentallydifferentiated fairway and port dues.Reduced dues primarily stimulate theferry traffic and other maritime traffic toand from Sweden, regardless of the ship’sflag state, to take measures which wouldbenefit the environment, such as usingcatalytic converters or making othertechnical improvements that decreasethe nitrogen oxide emissions and pro-mote the use of low-sulphur bunker fuel.

The environmental differentiation meansthat the ship-based portion of the fairwaydues is differentiated according to theship-generated emissions of nitrogenoxides and sulphur.

Basically, the authorities give a rebateon port dues when a ship reduces theemission level. As an example, a shipwill be given an additional rebate of SEK0.90 per unit of the ship’s gross tonnageif the sulphur content of the bunker fuelis lower than 0.5 mass percent for pas-senger ships, and 1.0 mass percent forother ships.

These environmentally differentiated fair-way and port dues came into force on1 January 1998.

NorwayThe Norwegian Maritime Directorate is-sues guidelines on emission limits. Thelimits do not apply to all ship types andare based on a calculation of the totalemission load factors from NOX, SOX,the type of fuel, and the use of redundantmachinery. The higher the emissionfactor, the better the protection of theenvironment, and the less is to be paidin tonnage tax by Norwegian ownersand operators. This rule became effectiveon 28 November 2000, and applies toships above 1000 net register tons.

New EPA emission rulesTier 1Valid for all marine engines larger than30 litres (category-3 engines).

Valid only for US flag ships built after 1January 2004, and for existing shipswhich have had new engines installed.

The NOx emission level is in accordancewith the IMO Annex VI speed curve.EPA will issue certificates, Marine Clas-sification Societies or Survey Societieswill not be authorized to do so.

In Tier 1, there are no limitations onCO, CO

2, HC, particulate and smoke.

EPA does not set sulphur limits in Tier1, however, EPA is planning to designatepart of the US coastline as a low-sulphurrestricted area once the IMO Annex VIhas been enforced.

EPA has adopted the IMO compliancerules with only minor exceptions, i.e.the technical file and survey programme,however, minor additional work is ne-cessary, incl. an operation manual.

The manufacturer is responsible fordemonstrating that the engine canmeet the emissions standards through-out its useful life which, in EPA terms,corresponds to three years, or 10,000hours of operation, and which may notbe less than any mechanical warrantythat the manufacturers offer for theengine (extended guarantee andsubcon engines).

Manufacturers must include a deterio-ration factor for emission control com-ponents throughout the engine’s usefullife (three years).

Tier 2Tier 2 is the next step to be adopted nolater than 27 April 2007, with a state oftechnology that may permit deeperemission reduction. This may also applyto non-US flag ships.

An approx. 30% reduction below IMOAnnex VI NOx limits is being considered.In Tier 2, limits to emissions like SO

xHC, CO and particulates are expected.

20

Unified Technical File

MAN B&W Diesel has, since the publi-cation of the IMO Technical Code in 1997,worked together with the licensees andclassification societies (representativesfor flag states) to find a uniform designof the technical files (TF) required underIMO’s Annex VI in order to survey com-pliance on board.

The technical file being the technical testtrial’s documentation for a specific engineor engine family.

Many of the first TFs produced by theengine builders were based on differentdemands made by the different classifi-cation societies and, therefore, theywere not consistent. Basically, this isbecause the IMO Annex VI does notgive sufficiently detailed instructions onhow to draw-up the TF in practice.

As a licensor, MAN B&W Diesel has assuch assumed the task of coordinatingthe work to prepare a uniform TF to beused both by the licensees and theclassification societies. The task in-cludes the necessary procedures forship owners, if later engine adjustmentor changes of components becomenecessary.

The advantages of using the unifiedMAN B&W Diesel TF are as follows:

• Certainty of market acceptance ofthe TF

• Satisfied customers who are able toshow engine compliance when checkedat sea by the flag state

• A survey method based on principlesfamiliar to the crew onboard

• More engines can be accepted withinthe same groups, thus resulting in re-duced expenses

• Less money spent on emission mea-surements

• Parent engines can be shared betweenMAN B&W licensees, which will greatlyreduce the number of emission mea-surements and future certification costs.

Design of Technical FileThe principle of the MAN B&W Dieselunified concept is that the performancedata (i.e. measurements of p

max, p

comp,

pscav

, Tscav

and pback

) can show whetheran engine complies with the NO

x limit.

If the operator has changed compo-nents or adjusted the engine, the en-gine will be out of compliance when theengine is later checked by the flag statefor compliance at sea, unless extensivetestbed testing is performed to validatethese changes.

For current testbed and sea trial compli-ance tests, this is not a major problem,but the issue will be much more impor-tant when the IMO Annex VI is ratified,and focus will be on follow-up at sea,where changes and adjustments willtake place.

From time to time, some ship ownerscontact MAN B&W Diesel about theseissues, and some owners have alreadydemanded a unified system in order toavoid working with different TFs, de-pending on which licensee and classifi-cation society were involved in an MANB&W engine delivery.

At sea, in case a ship owner changescomponents, this unified system willalso allow change of the engine’s NOx

components while maintaining IMOcompliance.

Summary:The unified TF is the standard TF intro-duced by MAN B&W Diesel and ac-cepted by the relevant classification so-cieties’ headquarters and introduced tolicensees for all future engines built.

Assistance from MAN B&W DieselIn case of any questions regarding theapplication of the TF, please contactMAN B&W Diesel, dept. 2110. The de-tailed description of the survey methodscan be found in the TF (Chapter 3 andAppendix B).

21

Conclusions

The development of new measuringequipment for emission control will con-tinue in the coming years, and especiallytechniques like HAM and EGR will befurther developed and tested. The con-cern of local authorities will change fromfocussing on NOx and SOx to include alsosmoke, in particular, and CO2.

The IMO Annex VI was ratified in 2004and, thereby, an international exhaustgas emission limit for ships will be intro-duced, but more local rules may also beintroduced.

Local rules that encourage the use ofemission cutting means, such as SCRreactors, through harbour fee reduc-tions can become more dominant thantoday, whereas an international rule is pre-ferred by the industry on the ground that theemission cutting means on board are thesame wherever a ship is operating andtrading. SCR units are preferably in-stalled during the construction of thevessel, however, as seen on the NavionDania, retrofitting is also possible.

MAN B&W Diesel has introduced a uni-fied technical file for the licensee andthe engine builder after acceptancefrom the relevant headquarters of theclassification societies’ representing theflag state in connection with the Annex VIemission code.

The challenge to shipowners will increaseas vessels are required to have, or beprepared for, emission control equipment.The sulphur content in fuel will have to bereduced, and vessel tank systems willhave to be prepared for dual fuel anddual cylinder lube oil systems. In someareas, the operating profile of the shipwill have to be adapted to local rules forreduced smoke emission. MAN B&WDiesel A/S makes every effort to facili-tate adaptation to emission regulationsfor engine builders, yards and shipowners,with a view to achieving the global tar-get of a cleaner planet. The latest gen-eration of electronically controlled en-gines are an integral part of that policy,as is our recommendation for use oftwo-stroke diesel engines as primemovers for LNG ships instead of steamturbines.

References

[1] “Emission control, two-stroke low- speed diesel engines”, paper pub- lished by MAN B&W Diesel A/S, Copenhagen, December 1996

[2] “NOx control in practice and demands

made on owners and engine builders”, MAN B&W Diesel paper for meet- ing at the Maritime Museum in Bergen, March 2000

[3] “NOx Emission Reduction with the

Humid Motor Concept”, 23rd CIMAC Congress, Hamburg, April 2001.

[4] “Soot Deposits and Fires in Exhaust Gas Boilers”, paper published by MAN B&W Diesel A/S, Copenhagen.

[5] “LNG Carrier Propulsion by ME-GI Engines and/or Reliquefaction” Sept. 2003